#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int jishu(int n)
{
	int kong = 0;
	int shu = 0;
	shu = n;
	kong = shu;
	while (kong > 1)
	{
		kong = kong - 2;
		shu = shu + 1;
		kong = kong + 1;
	}
	return shu;
}
int main()
{
	int n;
	scanf("%d", &n);
	printf("%d", jishu(n));
	return 0;
}